Not Applicable
The present invention is directed generally to electrical equipment. More particularly, the invention relates to optical and electrical systems having line cards with connections to input and/or output lines. The continued growth in traditional communications systems and the emergence of the Internet as a means for accessing data has accelerated demand for high capacity communications networks. Telecommunications service providers, in particular, have looked to higher capacity and performance communications equipment to handle the increased volume of communications traffic.
For example, service providers have looked to wavelength division multiplexing (xe2x80x9cWDMxe2x80x9d) to provide higher capacity transmission systems. In WDM transmission systems, pluralities of distinct information signals are carried using electromagnetic waves having different wavelengths in the optical spectrum, typically in the infrared range. Each information carrying wavelength can include a single data stream or multiple data stream that are time division multiplexed (xe2x80x9cTDMxe2x80x9d) together into a TDM data stream. 1 the pluralities of information carrying wavelengths are combined into a multiple wavelength, xe2x80x9cWDMxe2x80x9d, optical signal that is transmitted in a single waveguide. In this manner, WDM systems can increase the transmission capacity of existing space division multiplexed (xe2x80x9cSDMxe2x80x9d), i.e., single channel, systems by a factor equal to the number of wavelengths used in the WDM system.
A difficulty that exists with higher capacity systems is the amount of equipment that is necessary to process the various signals being transmitted through the networks. The equipment generally is deployed on line cards, which are placed side-by-side in one or more shelves supported in a rack.
While it is desirable to minimize the space occupied by the components in the system, or footprint, various component properties affect the spacing in a system. In addition to physical size limitations on component spacing, other properties, such as heat generation and dissipation and electromagnetic radiation and conduction by the components affect the spacing.
For example, the input and output ports of the line cards provide a significant leakage path for electromagnetic radiation that can result in electromagnetic interference (xe2x80x9cEMTxe2x80x9d) with surrounding electrical equipment. As a result, it is often not possible to mount electrical and optical components that radiate a significant amount of electromagnetic waves near the input and output ports of the line cards. EMI gaskets and small apertures have been used in the past to attenuate the level of the RF energy to within allowable levels per Telcordia GR-1089, which is incorporated herein by reference, and 19 other industry standards. These efforts have met with qualified success depending upon the component placement on the line cards relative to the ports. The continuing development of electrical and optical technologies will produce physically smaller components. The decrease in physical size will tend to exacerbate these other properties, which will continue to pose a substantial impediment to deploying optical and electrical equipment with smaller footprints. As such, there is a need to improve continually the physical design and packaging of electrical and optical equipment at the component, line card, shelf, and rack level for use in higher performance optical and electrical subsystems and systems.